MAINTAINERS: Update GRUB git repository and mailing list addresses

We are announcing the new place where the GRUB repository [1] will be
hosted and its corresponding mailing list [2]. The repository at
freedesktop [1] would become soon the upstream repository, so new
contributions will need to be done through merge-requests.

The decision to migrate to a more modern repository system (freedesktop
is indeed a gitlab instance) is clear and based on several proposed
options, freedesktop turned out to be the best option. More information
about this migration is coming soon.

[1] https://gitlab.freedesktop.org/gnu-grub/grub/
[2] https://lists.freedesktop.org/postorius/lists/grub-devel.lists.freedesktop.org/

Signed-off-by: Leo Sandoval <lsandova@redhat.com>
Signed-off-by: Marta Lewandowska <mlewando@redhat.com>
Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Andrew Hamilton <adhamilt@gmail.com>

MAINTAINERS

@@ -14,10 +14,9 @@ file to get more information how to properly report this kind of bugs to
 the maintainers.
 
 The GRUB development happens on the grub-devel mailing list [1]. The latest
-GRUB source code is available at Savannah git repository [2].
+GRUB source code is available at freedesktop git repository [2].
-
-Users can ask for help on the help-grub mailing list [3].
 
+Users can also ask for help on the same grub-devel mailing list [1].
 
 List of past GRUB maintainers and people who strongly contributed to the project
 ================================================================================
@@ -32,6 +31,5 @@ strongly contributed to the project:
   - Yoshinori K. Okuji.
 
 
-[1] https://lists.gnu.org/mailman/listinfo/grub-devel
+[1] https://lists.freedesktop.org/postorius/lists/grub-devel.lists.freedesktop.org/
-[2] https://git.savannah.gnu.org/gitweb/?p=grub.git&view=view+git+repository
+[2] https://gitlab.freedesktop.org/gnu-grub/grub/
-[3] https://lists.gnu.org/mailman/listinfo/help-grub